Entity Framework One To Many Relationship mapping foreignkey causing null on navigation properties

Question

I'm trying to build relationship while wanted to specify child and parent tables foreign key in addition to navigation property, model looks like this

public class Parent
{
    public Parent()
    {
        this.Childern = new HashSet<Child>();
    }
    public Guid Id { get; set; }

    public string Name { get; set; }

    //public Guid Child_Id { get; set; } 

    public ICollection<Child> Childern { get; set; }
}

public class Child
{
    public Child()
    {
        this.Parent = new Parent();
    }
    public Guid Id { get; set; }

    public string Name { get; set; }

    public Guid Parent_Id { get; set; }
    public Parent Parent { get; set; }
}

With only above model when i build and run project, i get expected results on navigation properties as navigation properties are populated with expected data. But i get additional un-wanted column in database as below

Id
Name
Parent_Id
Parent_Id1 (FK)

I further configured relationship in OnModelCreating like below

    modelBuilder.Entity<Child>()
    .HasRequired(p => p.Parent)
    .WithMany(p => p.Childern)
    .HasForeignKey(k => k.Parent_Id);

This time I got desired result on table structure now table looks like this

Id
Name
Parent_Id (FK)

But I'm getting null on navigation properties, please note that I'm trying Eagerly Loading

    public static void TestParent()
    {
        using (var context = new ILDBContext())
        {
            var parents = context.Parents
                .Include(p => p.Childern)
                .ToList();

            foreach (var parent in parents)
            {
                Console.WriteLine("Parent: {0} Childern: {1}", parent.Name, parent.Childern.Count());
                foreach (var child in parent.Childern)
                {
                    Console.WriteLine("Child: {0}", child.Name);
                }
            }
        }
    }

In addition I will be thankful if anyone can advise how should i configure relationship if i need FK in both models like, Parent_Id and Child_Id Thanks.

Try marking your collection virtual and don't new it up. See this: http://stackoverflow.com/questions/20757594/ef-codefirst-whether-initialize-navigation-properties — Steve Greene, Mar 21 '16 at 18:06
I did try virtual but it does't work, there is something wrong with my relationship statement in OnModelCreating, because without this i get results. — sairfan, Mar 21 '16 at 19:39

score 1 · Accepted Answer · answered Mar 21 '16 at 18:06

1

You need to remove the Parent assignment in your Child constructor:

public Child()
{
    this.Parent = new Parent();
}

has to be

public Child() {}

or you don't define it at all. For the ICollection<Child> in your Parent it doesn't really make a difference.

answered Mar 21 '16 at 18:06

Alexander Derck

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Thanks it works, can you please explain. Why it preventing loading navigation properties? Thanks. – sairfan Mar 21 '16 at 21:38
In the constructor you are immediately assigning another parent (empty one) to the navigation property. EF doesn't overwrite the behavior in constructor – Alexander Derck Mar 21 '16 at 21:39

Entity Framework One To Many Relationship mapping foreignkey causing null on navigation properties

1 Answers1